I. Field of the Invention
This invention relates generally to processes for preparing unsaturated alcohols. More particularly, the invention relates to vapor phase processes for preparing alpha, beta-ethylenically unsaturated alcohols from alpha, beta-ethylenically unsaturated aldehydes by direct hydrogenation.
II. Summary of the Prior Art
Processes for preparing alpha, beta-ethylenically unsaturated alcohols by the hydrogen reduction of alpha, beta-ethylenically unsaturated carbonylic compounds may be represented by the following equation: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 may be hydrogen or lower alkyl. Such, or similar processes, are described, for example, in U.S. Pat. No. 2,763,696 (Finch et al.), U.S. Pat. No. 2,767,221 (Ballard et al.), U.S. Pat. No. 3,655,777 (Rylander et al.), and Broadbent et al., J. Org. Chem. 24, 1844 - 54 (1959).
Processes for the vapor phase hydrogenation of alpha, beta-ethylenically unsaturated carbonylic compounds to alpha, beta-ethylenically unsaturated alcohols are disclosed in U.S. Pat. Nos. 2,763,696 and 2,767,221 but such processes suffer from the disadvantages of low selectivity as well as the need for relatively high reaction temperatures and pressures. Further, those processes which carry out the hydrogenation of alpha-beta unsaturated aldehydes in a liquid phase may be accompanied by undesirable polymerization reactions.
The search has continued for improved processes for preparing alpha, beta-ethylenically unsaturated alcohols by the vapor phase hydrogenation of alpha, beta-ethylenically unsaturated aldehydes. This invention was made as a result of that search.